The research objectives of this project have "analytical" and "synthetic" aspects. It is intended to use a variety of appropriate techniques in chronic and acute cats to describe quantitatively, and to attempt to explain in terms of synaptic inputs, the transformation of signals in the somatosensory and VL-VA projection systems to sensorimotor cortex, with special emphasis on the behavior of pyramidal tract neurons and their associated interneurons. It is intended to direct the experiments towards elucidating how portions of the overall thalamocortical system are interrelated in the performance of certain functions. The tactile placing reaction and certain voluntary movements are considered especially favorable types of behavior to attempt to explain in a synthesis. A related objective will be to account for the changes in activity of the same thalamocortical systems during sleep and waking. Subsidiary objectives are to use the neural substratum of the tactile placing reaction as a model system in studying recovery of function following lesions, in studying development of sensorimotor integration in the neonate and in studying the neurophysiological basis of plasticity.